lims, lims_report_html: avoid memory leak when plotting trend charts

lims/control_tendency.py

@@ -6,6 +6,7 @@ import pandas as pd
 from io import BytesIO
 from math import sqrt
 import matplotlib.pyplot as plt
+import gc
 
 from trytond.model import ModelView, ModelSQL, fields
 from trytond.wizard import (Wizard, StateTransition, StateView, StateAction,
@@ -1979,8 +1980,14 @@ class TrendChart(ModelSQL, ModelView):
                     i += 1
 
                 ax.get_figure().savefig(output, bbox_inches='tight', dpi=300)
+                plt.close('all')
                 image = output.getvalue()
                 output.close()
+            # release memory
+            del ax, df, df_interpolated
+            if ds2:
+                del df2, df2_interpolated
+            gc.collect()
             return image
 
         except (TypeError, ModuleNotFoundError):
@@ -2013,12 +2020,23 @@ class TrendChart(ModelSQL, ModelView):
 
                     ax.get_figure().savefig(output, bbox_inches='tight',
                         dpi=300)
+                    plt.close('all')
                     image = output.getvalue()
                     output.close()
+                    # release memory
+                    del ax, df, df_interpolated
+                    if ds2:
+                        del df2, df2_interpolated
+                    gc.collect()
                     return image
 
                 except (TypeError, ModuleNotFoundError):
                     pass
+            # release memory
+            del df, df_interpolated
+            if ds2:
+                del df2, df2_interpolated
+            gc.collect()
             return output.getvalue()
 
     @classmethod

lims_report_html/html_template.py

@@ -431,9 +431,12 @@ class LimsReport(Report):
             for section in record.following_sections:
                 filedata = BytesIO(section.data)
                 merger.append(filedata)
+            filedata.close()
             output = BytesIO()
             merger.write(output)
+            merger.close()
             document = output.getvalue()
+            output.close()
 
         return 'pdf', document
 

lims_report_html/results_report.py

@@ -417,6 +417,7 @@ class ResultsReportVersionDetailSample(metaclass=PoolMeta):
             open_chart.transition_compute()
             plot = tc.chart.get_plot(session_id)
             charts.append(plot)
+            OpenTrendChart.delete(session_id)
 
         div_row = '<div style="clear:both;">'
         charts_x_row = int(self.version_detail.charts_x_row) or 1
@@ -464,6 +465,7 @@ class ResultsReportVersionDetailSample(metaclass=PoolMeta):
             open_chart.transition_compute()
             plot = tc.chart.get_plot(session_id)
             charts.append(plot)
+            OpenTrendChart.delete(session_id)
         return charts
 
     def _get_resource(self, obj):